Electrical characterisation of fermentation process from milk to yogurt: a monitoring approach

This study investigates the changes in electrical properties (electrical conductivity and dielectric capacitance) during yogurt fermentation, correlating them with traditional measurements (pH and titratable acidity) and rheological properties (gel strength and textural parameters) for monitoring purposes. The results show a significant linear relationship between electrical conductivity vs. time as well as capacitance vs. time (R² = 0.95), outperforming the pH-time trend. It was observed that yogurt made from cow milk with 4% fat had electrical conductivity and capacitance values of 10.29 ± 0.45 mS/cm and 632.85 ± 9.32 µF, respectively, when it reached to pH 4.6 ± 0.03, i.e. end of fermentation. Capacitance exhibits a stronger association with textural parameters (firmness, cohesiveness, consistency, and work of cohesion) compared to electrical conductivity. The changes in gel strength parameters reveal the transition from Newtonian (viscous behavior of milk) to non-Newtonian (viscoelastic behavior of yogurt) behavior during fermentation. Analyzing the electrical properties of yogurt samples at various fermentation stages reveals a clear relationship between these properties and fermentation progression. This study could provide a rapid and non-invasive technique for real-time monitoring of yogurt fermentation, potentially enabling more efficient quality control and process optimization in yogurt production.